This project seeks to determine the dose and the method of injection of ricin, which will permanently reduce eyelid and oculo-rotary muscle function in the rabbit without excessive adverse local or systemic side effects. Reduction in muscle size, muscle regeneration, and other effects on the target muscle will be assessed by functional tests and by light and electronmicroscopy. Effect on adjacent tissues will be assessed by clinical examination and by histology. Effects of neuron transport to and within the central nervous system will be assessed by histology. Systemic effects will be monitored by tests of liver, renal and cardiac function and by histology of these organs. If these experiments are successful, this approach and these data will form the basis of an experimental, clinical drug treatment for focal dystonias.